The present invention relates to a plasma display panel (PDP) and a driving method of the PDP, in particular, which is operated by an alternating current (AC).
A PDP, a liquid crystal display (LCD), and an electro-luminescence display (ELD) are used as a flat display panel. The PDP has been used for a work station and a wall television set, as a display whose screen size can be made to be large. Recently, a PDP whose screen size is large, for example, a 40 inch-type or a 50 inch-type PDP has been realized. However, it is very difficult that a cathode ray tube (CRT) technology realizes this size of screen.
It is expected that the CRT display will be replaced by the PDP in the future, however, its cost is higher and also its power consumption is larger than those of the CRT display.
The PDP provides plural display cells arrayed in a matrix state. There are two light emitting systems at the PDP, that is, one is a direct current driving type (DC type) and the other is an alternating current driving type (AC type). At the DC type, electrodes are exposed in a discharge space filled with a discharge gas, and DC voltages are applied to the electrodes. At the AC type, the electrodes are covered with a dielectric layer and are not directly exposed in the discharge gas, and AC voltages are applied to the electrodes. Further, the AC type is classified into two types, that is, one type is a memory utilizing type that utilizes a memory function of the dielectric layer which stores electric charges, and the other type is a refreshing type that does not utilizes the memory function.
A conventional PDP provides a front substrate and a rear substrate facing the front substrate, and a designated interval exists between the front substrate and the rear substrate. Plural scanning electrodes and plural common electrodes are disposed in parallel in the row direction on the front substrate. Plural data electrodes are disposed in the column direction on the rear substrate.
The display cells (pixels), which are formed at points where the data electrodes cross the scanning electrodes and the common electrodes, emit light by making discharges generate by that a designated voltage is applied to each of the electrodes under designated conditions. The scanning electrodes and the common electrodes are covered with a first dielectric layer on whose surface a protection layer is formed, and the data electrodes are covered with a second dielectric layer on whose surface a designated fluorescent material is coated. With this structure, an image is displayed on the PDP.
FIG. 1 is a timing chart of driving voltage waveforms in one sub field (SF) at a driving method of a conventional memory utilizing type AC-PDP. As shown in FIG. 1, the 1 SF consists of a priming discharge period, a scanning period, and a sustaining period. At the priming discharge period, erasing pulses 21, priming discharge pulses 22, and priming discharge erasing pulses 23 are applied. At the scanning period, scanning pulses 24, and data pulses 27 are applied. And at the sustaining period, sustaining pulses 25 and 26 are applied.
In FIG. 1, the conventional memory utilizing type AC-PDP provides xe2x80x9cmxe2x80x9d scanning electrodes Si(i=1, 2, . . . , m), xe2x80x9cmxe2x80x9d common electrodes Ci(i=1, 2, . . . , m), and xe2x80x9cnxe2x80x9d data electrodes Dj(j=1, 2, . . . , n), and each of the xe2x80x9cmxe2x80x9d scanning electrodes Si becomes a pair with each of the xe2x80x9cmxe2x80x9d common electrodes Ci. And each of the display cells is formed at a point where each of the data electrodes Dj crosses each of the scanning electrodes Si and each of the common electrodes Ci.
First, at the priming discharge period, the erasing pulses 21 are applied to all of the scanning electrodes 12, and discharging is generated at display cells in discharge ON state, which have emitted light during the previous sustaining period, and all of the display cells are made to be an erasing state (discharge OFF state). This operation by the erasing pulses 21 is called as sustaining discharge erasing operation. In this, the erasing signifies that wall charges are decreased or made to be zero. The wall charges are explained in detail later.
Next, the priming discharge pulses 22 are applied to all of the common electrodes 13, and discharging is generated at all of the display cells by compulsion. And the priming discharge erasing pulses 23 are applied to all of the scanning electrodes 12, and all of the display cells are made to be an erasing state. In this, discharging operation by the priming discharge pulses 22 is called as priming discharge operation, and discharging operation by the priming discharge erasing pulses 23 is called as priming discharge erasing operation. These priming discharge operation and priming discharge erasing operation make the occurrence of the following writing discharge easy.
After the priming discharge erasing operation, in the scanning period, a scanning pulse 24 is applied to the scanning electrodes S1 to Sm in sequence by shifting the applying timing of the scanning pulse 24. And the data pulses 27 corresponding to display information are applied to the data electrodes D1 to Dn respectively, by matching with the timing applying the scanning pulse 24. The oblique line attached to the data pulses 27 shows that the presence/absence of data pulses 27 is determined in accordance with presence/absence of the display information data. When the scanning pulse 24 was applied, discharging is generated only at display cells corresponding to the data electrodes 19, to which the data pulses 27 were applied. This discharge is called as the writing discharge, because the display information is written in the display cells when the discharge is generated.
At the display cell where the writing discharge was generated, a positive electric charge called a wall charge is stored in the dielectric layer on the scanning electrode 12, and a negative wall charge is stored in the dielectric layer on the data electrode 19.
In the sustaining period, the first discharge is generated at the display cell, by adding the first sustaining pulse 25 being negative polarity applied to the common electrode 13 to the positive wall charge in the dielectric layer on the scanning electrode 12. When the first discharge was generated, a positive wall charge is stored in the dielectric layer on the common electrode 13, and a negative wall charge is stored in the dielectric layer on the scanning electrode 12. And the second discharge is generated, by adding the second sustaining pulse 26 applied to the scanning electrode 12 to the potential difference between positive and negative wall charges. As mentioned above, the discharge is sustained by adding the (n+1)th sustaining pulse to the potential difference of the wall charges formed by xe2x80x9cnxe2x80x9dth discharge (n is an integer), therefore, this discharge is called as a sustaining discharge. The light emitting luminance is controlled by the number of continuing times of the sustaining discharges.
The sustaining pulse 25 to be applied to the common electrode 13 and the sustaining pulse 26 to be applied to the scanning electrode 12 are adjusted to be low voltages so that the discharge is not generated by only applying the sustaining pulses 25 and 26. With this, at a display cell, in which a writing discharge was not generated, electric potential by wall charges does not exist before the first sustaining pulse 25 is applied. Therefore, even when the first sustaining pulse 25 is applied, the first sustaining discharge is not generated at the display cell, and the sustaining discharge is not generated after this.
FIG. 2 is a timing chart of driving voltage waveforms in one SF at a conventional AC-PDP described in Japanese Patent No. 2503860. At the driving voltage waveforms shown in FIG. 2, a sub scanning pulse 28 being negative polarity is applied to all of the common electrodes 13 in the scanning period. Driving pulses in the priming discharge period and the sustaining period are the same as those in FIG. 1, therefore, the same explanation is omitted.
At the writing discharge in a conventional AC-PDP, by applying the scanning pulses 24 to the scanning electrodes 12 and also applying the data pulses 27 to the data electrodes 19, display cells are selected and discharges are generated at the selected display cells. However, in order to generate the writing discharge surely, when the voltage of the scanning pulse 24 is made to be high, at a part of the display cells, to which only the scanning pulses 24 were applied, there was a case that an error discharge was generated between the scanning electrode 12 and the common electrode 13. A part of the display cells, discharged erroneously, was shifted to the sustaining discharge, and light was emitted from a display cell, which was not to be selected normally.
In order to solve this problem, at the Japanese Patent No. 2503860, the sub scanning pulse 28 being negative polarity is applied to all of the common electrodes 13 in the scanning period. By applying the sub scanning pulse 28 being negative polarity, the potential difference between the scanning electrode 12 and the common electrode 13 in the scanning period is made to be small. With this, the voltage value of the scanning pulse 24 can be made to be a high value that is necessary for the writing discharge, without the error discharge.
And also, in the Japanese Patent No. 2503860, it has been described that a sub scanning pulse being positive polarity (not shown) is applied to all of the common electrodes 13 in the scanning period. At the writing discharge, a discharge generating selectively between the scanning electrode 12 and the data electrode 19 (facing discharge) is made to be a trigger, and right after this, a discharge between the scanning electrode 12 and the common electrode 13 (surface discharge) is induced. With this, shifting to the sustaining discharge after the scanning period is made to be sure.
Further, in this Japanese Patent No. 2503860, various driving voltage waveforms in the priming discharge period, being different from those shown in FIGS. 1 and 2, have been proposed, at the cases that the structures of the display cells of the PDP are different and also the states after the priming discharge are different. And either the sub scanning pulse being negative polarity to prevent the error discharge or the sub scanning pulse being positive polarity to improve the shift to the sustaining discharge is adopted for being effective at the adopted structure and the state. In this patent, the sub scanning pulse 28 being negative polarity is used for preventing the error discharge.
FIG. 3 is a diagram showing a gray level displaying method at a conventional AC-PDP. As shown in FIG. 3, one field being a period in which one picture is displayed is divided into plural sub fields (four sub fields in FIG. 3). In this, the period, in which one picture is displayed, is a time that eyes of a human being does not recognizes a picture as a flicker, and is a period being less than {fraction (1/36)} second, for example, about {fraction (1/60)} second. In FIG. 3, each of sub fields SF1 to SF4 is composed of the priming discharge period, the scanning period, and the sustaining period, and the length of each sustaining period (the number of sustaining pulses) is different from one another. The luminance of display among the SFs is different from one another, and each of the sub fields can be turned on/off independently.
At the four sub fields shown in FIG. 3, in case that the luminance ratio is adjusted to 1:2:4:8 in the SF1 to SF4, when light is emitted from each of the SF1 to SF4 independently, 16 levels of the luminance can be displayed. That is, by the combination of the displaying on/off of the four SFs, the 16 levels of the luminance, from the luminance ratio 0 at the time when all of the SFs are not selected to the luminance ratio 15 at the time when all of the SFs are selected, can be displayed. Generally, when one field is divided into xe2x80x9cnxe2x80x9d sub fields, and the luminance ratio is set to be 1(=20):2(=21): . . . :2nxe2x88x922:2nxe2x88x921, 2n gray levels can be displayed.
At the conventional AC-PDP, in order to generate the writing discharge surely, it is necessary that the pulse width of the scanning pulse 24 is made to be large. Consequently, the scanning period, which is shown as the product of the width of the scanning pulse and the number of the scanning electrodes, becomes long, and a time, which can be used for the sustaining period in one SF, becomes short. Therefore, there is a problem that the light emitting luminance is lowered.
In order to solve this problem, in Japanese Patent No. 2962039, a technology, in which a time requiring for the writing discharge is shorten by improving a display cell structure, has been described. In this technology, a structure, in which the area of the data electrode being effective for the writing discharge is made to be large, was adopted. However, the manufacturing processes must be changed by the change of the display cell structure and there is a problem that the yielding ratio at manufacturing the PDP is decreased due to the complex display cell structure.
In Japanese Patent Application Laid-Open No. HEI 10-149133, a technology, in which the time interval from the priming discharge erasing to the writing discharge is shortened and the writing discharge is made to be high speed by that the priming discharge erasing pulse is inputted right before the writing discharge, has been described. However, at this technology, there is a problem that a special driver for inputting the priming discharge erasing pulse is required.
In Japanese Patent Application Laid-Open No. HEI 5-250995, a technology, in which auxiliary discharge cells are provided in addition to the display cells and the writing discharge is made to be high speed by generating discharge at the auxiliary discharge cells right before the writing discharge at the display cells, has been described. However, at this technology, there are problems that the PDP structure is made to be complex and its high resolution is not realized easily by providing the auxiliary discharge cells.
In Japanese Patent Application Laid-Open No. HEI 4-241383, a technology, in which a high potential pulse is added to a data pulse for making the writing discharge easy at the display cell at only the time when the writing discharge was not generated before one scanning pulse cycle at the adjacent display cell to the display cell, has been described. However, at this technology, there is a problem that a driving circuit for processing signals to output the high potential pulse corresponding to the state of the adjacent display cell to the display cell is newly required in addition to the data pulse corresponding to the on/off information at the display cell.
It is therefore an object of the present invention to provide a PDP and a driving method of the PDP, in which a special change for the structure of the current PDP is not required and only a slight change for the driving circuit of the current PDP is executed and the writing discharge can be executed stably by using scanning pulses whose width is small, and in which the light emitting luminance is made to be high by extending the sustaining period in one SF, and in which the high resolution can be obtained and the yielding ratio at the manufacturing is high.
According to a first aspect of the present invention, for achieving the object mentioned above, there is provided a PDP driving method. The PDP at the PDP driving method provides a first substrate having a plane shape and a second substrate having a plane shape which faces the first substrate, plural first row electrodes and plural second row electrodes arrayed in the row direction on the first substrate, plural column electrodes arrayed in the column direction on the second substrate, and plural display cells disposed at points where the plural column electrodes cross the plural first and second row electrodes. And the PDP driving method provides the steps of applying a scanning pulse to each of the plural first row electrodes by shifting the applying timing of the scanning pulse by a designated interval in a scanning period, writing display information in each of the plural display cells by applying a data pulse to each of the plural column electrodes by making the data pulse synchronize with the scanning pulse in the scanning period, making a sustaining discharge generate at only display cells selected corresponding to the display information by applying a sustaining pulse to the plural first and second row electrodes in a sustaining period, and making the selected display cells emit light. And the PDP driving method further provides the steps of applying a sub scanning pulse to the plural second row electrodes in the scanning period, making display cells, which do not generate the sustaining discharge later in the sustaining period, generate a writing discharge having first intensity by applying a scanning pulse to each of the plural first row electrodes in the scanning period, and making display cells, which generate the sustaining discharge later in the sustaining period, generate a writing discharge having second intensity by applying a scanning pulse to each of the plural first row electrodes and further by applying the data pulse to the plural column electrodes in the scanning period.
According to a second aspect of the present invention, in the first aspect, when the scanning pulse was applied to each of the plural first row electrodes, the writing discharge having first intensity is made to generate in the display cells, which do not generate the sustaining discharge later, by applying a data pulse having a first crest value, and the writing discharge having second intensity is made to generate in the display cells, which generate the sustaining discharge later, by applying a data pulse having a second crest value.
According to a third aspect of the present invention, in the second aspect, the first crest value is lower than the second crest value.
According to a fourth aspect of the present invention, in the third aspect, the data pulse having the first crest value is applied to all of the column electrodes in a bias state during almost all the scanning period, and a modulation voltage value is added to the column electrodes corresponding to display cells that generate the sustaining discharge later so that the voltage value applying to the column electrodes becomes the second crest value.
According to a fifth aspect of the present invention, in the first aspect, a scanning pulse cycle, which is the time interval (ti+1xe2x88x92ti) in case that the timing when a scanning pulse is applied to the (i)th first row electrode is defined as ti and the timing when the scanning pulse is applied to the (i+1)th first row electrode is defined as ti+1, is less than 2xcexc seconds.
According to a sixth aspect of the present invention, in the first aspect, the writing discharge having first intensity is weaker than the writing discharge having second intensity.
According to a seventh aspect of the present invention, in the first aspect, the pulse width of the scanning pulse applying to the first electrode in the plural first row electrodes is wider than that applying to electrodes following the first electrode, and also the pulse width of the data pulse synchronizing with the scanning pulse applying to the first electrode in the plural first row electrode, is wider than the others, in the scanning period.
According to an eighth aspect of the present invention, in the first aspect, the crest value of the scanning pulse applying to the first electrode of the plural first row electrodes is larger than that applying to electrodes following the first electrode, in the scanning period.
According to a ninth aspect of the present invention, in the first aspect, a priming discharge and a priming discharge erasing are applied to the display cells at the first electrode in the plural first row electrodes to which the scanning pulse is applied, and the priming discharge and the priming discharge erasing are not applied to display cells following the display cells at the first electrode, in the scanning period.
According to a tenth aspect of the present invention, in the first aspect, the sub scanning pulse is negative polarity.
According to an eleventh aspect of the present invention, in the first aspect, a bias voltage being positive polarity is applied to the column electrodes in almost all the scanning period.
According to a twelfth aspect of the present invention, there is provided a PDP. The PDP provides a first substrate having a plane shape and a second substrate having a plane shape which faces the first substrate, plural first row electrodes and plural second row electrodes arrayed in the row direction on the first substrate, plural column electrodes arrayed in the column direction on the second substrate, and plural display cells disposed at points where the plural column electrodes cross the plural first and second row electrodes. And a scanning pulse is applied to each of the plural first row electrodes by shifting the applying timing of the scanning pulse by a designated interval in a scanning period, display information is written in each of the plural display cells by applying a data pulse to each of the plural column electrodes by making the data pulse synchronize with the scanning pulse in the scanning period, a sustaining discharge is made to generate at only display cells selected corresponding to the display information by applying a sustaining pulse to the plural first and second row electrodes in a sustaining period, and the selected display cells emit light. And a sub scanning pulse is applied to the plural second row electrodes in the scanning period, and display cells, which do not generate the sustaining discharge later in the sustaining period, are made to generate a writing discharge having first intensity by applying the scanning pulse, and display cells, which generate the sustaining discharge later in the sustaining period, are made to generate a writing discharge having second intensity by applying the scanning pulse and the data pulse.
According to a thirteenth aspect of the present invention, in the twelfth aspect, when the scanning pulse was applied to each of the plural first row electrodes, the writing discharge having first intensity is made to generate in the display cells, which do not generate the sustaining discharge later, by applying a data pulse having a first crest value, and the writing discharge having second intensity is made to generate in the display cells, which generate the sustaining discharge later, by applying a data pulse having a second crest value.
According to a fourteenth aspect of the present invention, in the thirteenth aspect, the first crest value is lower than the second crest value.
According to a fifteenth aspect of the present invention, in the twelfth aspect, the pulse width of the scanning pulse applying to the first electrode in the plural first row electrodes is wider than that applying to electrodes following the first electrode, and also the pulse width of the data pulse synchronizing with the scanning pulse applying to the first electrode in the plural first row electrodes, is wider than the others, in the scanning period.
According to a sixteenth aspect of the present invention, in the twelfth aspect a priming discharge and a priming discharge erasing are applied to the display cells at the first electrode in the plural first row electrodes to which the scanning pulse is applied, and the priming discharge and the priming discharge erasing are not applied to display cells following the display cells at the first electrode, in the scanning period, and the number of the plural first row electrodes and the number of the plural second row electrodes are increased, and the number of the display cells is increase.